Deterioration Of Cables Research Articles

Thermal Aging Evaluation of XLPE Power Cable by Using Multidimensional Characteristic Analysis of Leakage Current.

Thermal aging is a common form of cable deterioration. In this paper, the effect of thermal aging on cables is evaluated by analyzing the harmonic characteristics in cable leakage currents. Cable samples were first fabricated and subjected to accelerated thermal aging tests at 120 °C. The experimental circuits were built to test the dielectric loss factor and the AC leakage current of the cable at different aging times. Then, the improved variational modal decomposition (VMD) algorithm was used for the time–frequency analysis of the leakage current, and the relationship between thermal aging and leakage current harmonics was investigated. Thermal aging was discovered to increase the capacitance and dielectric loss factor of the cable as well as generate harmonics in the leakage current, with harmonics at 150, 450, and 650 Hz being particularly sensitive to thermal aging. The multidimensional characteristic parameters such as the time-domain, frequency-domain, and relative energy and the sample entropy of the leakage current harmonics were calculated. The results demonstrated thermal aging increased the relative energy and power spectrum energy of the harmonics and increased the disorder of the harmonic sequence.

Experimental Investigation of Leakage Current in Power Cables under Different Operating Conditions.(Dept.E)

This paper reports an expermintal investigation into the effect of different factors on the leakage current in power cables. The leakage current of different cables was studied using installed cables under actual operating conditions and also cable samples in HV-laboratory under well-controlled conditions. The results obtained showed that, the leakage current in any power cable depends on many factors, including the value and type of the applied voltage, time of voltage application, cable type and construction, and the type of the surrounding soil and its resistivity. These results showed also that leakage current in power cables can be considered as a predictor of the cable failure because it is a good indicator of the cable deterioration.

케이블의 배열형태에 따른 화재 위험성에 관한 연구

In this study, the thermal and flame propagation characteristics of cable in perforated cable tray used in a low voltage indoor distribution line were analyzed according to the arrangement of the cable using Light PVC sheathed circular cord(VCTF) cable. A thermocouple was attached to the inside and outside of the cable to measure the temperature. The cables were arranged in vertical and horizontal directions and, layered in triangular and rectangular shapes. As compared to the temperature inside a single cable, the temperatures increased when numerous cable were arranged in a horizontal direction and layered in triangular and rectangular shapes. The temperature inside the cables reached a peak of 305 ℃ when the current was twice the allowable current. At allowable current, the temperature increased to 62℃ when the cables were layered in a rectangular shape. This was close to the maximum permissible temperature for VCTF cable(i.e., 70 ℃). The insulation resistance of the VCTF cable declined dramatically in accordance with increases in temperature, which not only raised the risk of short circuit and ground faults but also accelerated the cable deterioration. The flame propagated at a velocity of 2.7 ㎝/sec in the vertical direction and 0.95 ㎝/sec in the horizontal direction at twice the allowable current. The faster propagation velocity in the vertical direction was due to the characteristics of flame and plume, which moved in an upward direction due to a buoyancy effect.

Fuzzy evaluation analysis and extraction of H‐N parameters for On‐site distribution cable

With the increasing usage of cross-linked polyethylene (XLPE) power cables, it is more and more important to grasp and manage their insulation status. Nowadays, the distribution cables in urban area are of huge numbers, so it is impossible to carry out the preventive test for every cable. Therefore, it is very helpful to determine cables' testing urgency in a scientific way. Meanwhile, the main cable diagnosis methods in China are insulation resistance and withstanding voltage test, but they are difficult to quantitatively determine cable insulation status. Aiming at solving above challenges, according to the cable fault records in recent years, fuzzy evaluation analysis combining with mutual information is utilised to determine the insulation testing urgency (ITU) based on cable information including service year, laying way, load type, and length. At the same time, frequency domain spectroscopy (FDS) is introduced to diagnose the on-site cable insulation status quantitatively. Its characteristic parameters, including instantaneous electric susceptibility, DC conductivity, and hopping conductivity, are extracted by improved Havriliak–Negami (H-N) model and studied to analyse the changing trend before and after cable deterioration. The results show that the lower ITU is, the higher testing urgency is. ITU also has negative correlation with FDS characteristic parameters.

Durability of the flame retardance of ethylene‐vinyl acetate copolymer cables: Comparing different flame retardants exposed to different weathering conditions

ABSTRACTScientific publications addressing the durability of the flame retardance of cables during their long‐term application are rare and our understanding lacks. Three commercial flame retardants, aluminum hydroxide, aluminum diethyl phosphinate (AlPi‐Et), and intumescent flame retardant based on ammonium polyphosphate, applied in ethylene‐vinyl acetate copolymer (EVA) model cables, are investigated. Different artificial aging scenarios were applied: accelerated weathering (UV‐irradiation/temperature/rain phases), humidity exposure (elevated temperature/humidity), and salt spray exposure. The deterioration of cables' surface and flame retardancy were monitored through imaging, color measurements, attenuated total reflectance Fourier transform infrared spectroscopy, and cone calorimeter investigations. Significant degradation of the materials' surface occurred. The flame retardant EVA cables are most sensitive to humidity exposure; the cable with AlPi‐Et is the most sensitive to the artificial aging scenarios. Nevertheless, substantial flame retardance persisted after being subjected for 2000 h, which indicates that the equivalent influence of natural exposure is limited for several years, but less so for long‐term use. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47548.

발전소에서 운전 중인 활선 6 kV CV 단심 cable의 도체온도에 따른 피복 표면온도 및 부하전류 특성 분석

발전소의 발전기에서 생산된 전기를 외부 단자로 공급하기 위하여 유일하게 사용되는 수단은 6 kV CV 단심 cable이다. 발전소에서 발생하는 여러 종류의 사고들 중에서 cable의 열화로 인한 화재 사고는 막대한 사회 경제적 손실을 초래한다. 설계부터 시공 및 관리를 더욱 철저히 해야 한다. 설치환경 및 사용 조건 부하량 등에 따라 차이가 있겠지만, 증설과정, 부적절한 설계 등으로 인하여 cable의 단면적이 부족할 경우가 발생하며, 운전 전류에 의하여 초과된 허용온도는 cable의 열화 상태를 초래한다. 우리는 cable의 사고를 체계적으로 감시 및 예방하기 위한 측정 장비를 개발, 한국서부발전 주식회사(Korea Western Power Co., Ltd.)에 설치하여 활선 cable을 진단하였다. 이 논문에서 우리는 cable이 설치되어 있는 주위환경 특히, 주위 온도에 따라 변동하는 cable의 피복표면의 온도를 측정하고 이에 따른 부하 전류를 검토한 결과를 제시한다. 실제 예로서 주위 온도가 <TEX>$40^{\circ}C{\sim}10^{\circ}C$</TEX>의 경우에 피복의 표면 온도와 부하전류의 특성을 연구한 결과를 제시한다. The only method used in the power stations in order to deliver generated electric power is 6 kV XLPE (or CV) single core cables. Among many kinds of accidents happening in the power stations, the outbreak of fire due to the deterioration of live cables causes enormous socioeconomic losses. From the installation of the cables, the management and diagnose should be thoroughly made. Even though it differs depending on the installations and usage conditions, the cross-sectional area of cables is in shortage. The excessive allowable temperature caused from the current causes the deterioration of cables. In order to prevent an unexpected breakdown of live cables, we have invented a device to monitor and diagnose the status of cables. We have installed our device in the Korea Western Power Co., Ltd.. In this paper, we present our research results in situ that we have obtained by measuring the temperature of sheath, changing with the surrounding circumstances, especially ambient temperatures. We also show our study results of characteristics for temperature of sheath surface and load current at the ambient temperatures of <TEX>$40^{\circ}C-10^{\circ}C$</TEX>.

EFFECT OF NANOPARTICLES ON WATER TREEING CHARACTERISTICS IN XLPE INDUSTRIAL I NSULATING MATERIALS

Water treeing is still now one of the main causes of cable deterioration and so, it is widely known that water treeing is the responsible for the reduction of the service life of polymeric cables. This paper has been studied the effects of adding various amounts of nanoparticles as ZnO, and Al2O3 on water treeing characteristics in XLPE industrial materials. This research has focused on studying development of the nano-composite materials performance with water tree growth resistance superior to the unfilled matrix, and has stressed particularly the effect of filler volume fraction on the water tree length and via various frequencies. Finally, this research aims to present a systematic and comparative study about the effect of adding nanoparticles to change dielectric insulation properties, and to understand the role effect of these nanoparticles in the industrial insulation materials which can make significant improvement in water tree resistance, life-time of insulation and decreasing the water tree length in the industrial insulation materials.

An expert system for XPLE cable deterioration diagnosis and life forecasting

The recent increase in the demand for power in urban areas has caused changes in the way power is supplied. Underground distribution systems have been introduced for convenience in urban areas and to prevent injuries in case of a crisis. As a result, many new types of power cables are being used. One type, XPLE cables (also called CV cables) have been rapidly taking the place of conventional cables such as OF or SL cables since the 1960s because of their relatively easy installation and maintainability. However, distribution cables used under severe environmental conditions deteriorate rapidly (due mainly to water treeing), and some cables experience insulation breakdown. Therefore, many diagnostic methods have been developed, though they have not been very effective. By combining methods, a high reliability can be achieved in comparison to the use of a single method. However, processing the data is difficult for on-site personnel, so many experts are required. But there is a lack of qualified experts, hence we have turned to the development of expert systems.

Factors That Affect XLP Medium Voltage Cable Performance

Manufacturing designs and techniques can be employed to guard against known mechanisms of cable deterioration. What are the parameters that will extend cable life? This article examines the factors affecting XLP cable performance.

Investigation of Cable Deterioration Inside Reactor Containment

The deterioration of polyethylene and polyvinyl chloride cable materials in the containment building of an operating nuclear reactor has been investigated. Since the maximum dose experienced by the cable materials was only 2.5 Mrad during about 12 yr of operating life, the extent of material degradation was surprising. Laboratory aging experiments on the two materials established that the cause of the material deterioration in the plant was radiation-induced oxidation. The degradation rate was correlated with local levels of radiation intensity. It was determined that strong synergisms of radiation and elevated temperature, and also dose-rate effects, lead to the surprisingly rapid degradation rates found with these materials. It is concluded that in the design of laboratory methods for aging and qualification testing of organic materials for use in a nuclear plant environment, the possible occurrence of dose-rate effects and synergisms needs to be taken into account.

A New Method of Investigating Cable Deterioration and Its Application to Service Aged Cable

Investigation of the radial variation in electrical and chemical characteristics of cable insulation between conductor and sheath is suggested as a valuable means for throwing new light on cable'deterioration in service. An apparatus is described for the rapid accurate measurement of power factor of individual paper tapes taken from cable. A method is given for determining the total oxidation products in the oil from the paper tapes, layer by layer, from sheath to conductor. The results obtained by applying these methods to several types of service aged cable are reported, together with the indications which they give of the relative importance of ionization and oxidation as aging factors.

A new method of investigating cable deterioration and its application to bervice-aged cable

IINVESTIGATION of the radial variation in electrical and chemical characteristics of cable insulation between conductor and sheath is suggested as a valuable means for throwing light on cable deterioration in service. A cell is described for the rapid accurate measurement of power factor of individual paper tapes taken from cable. A method is given for determining the total oxidation products in the oil from the paper tapes, layer by layer, from sheath to conductor. The results obtained by applying these methods to several types of service-aged cables are reported, together with the indications which they give of the relative importance of ionization and oxidation as aging factors.